This invention relates to an improved dry transfer decal and a method of manufacture for such a decal.
There are many applications for a high strength, well protected, strongly adherent label. Such labels are traditionally made by printing inks onto a self-adhesive base film and then overlaminating the printed matter with a further layer of clear film to cover and protect the printed inks from abrasion and weathering. FIG. 1 illustrates such a label.
Traditional materials for the base film or substrate are transparent or pigmented vinyl or polyester, and various types of natural or synthetic papers. The appropriate substrate is chosen to give the desired properties of color, opacity, elasticity, tensile strength, etc.
The over laminating material is, of necessity, clear and transparent and may have a gloss or matt surface. The associated adhesive for affixing the protective overlaminating layer must be compatible with the previously printed inks and the base layer.
The overlaminate may be applied by several different methods; e.g., (1) hot laminating using an adhesive that melts upon the application of heat; (2) cold laminating using a pressure sensitive adhesive; and (3) solvent based adhesive where the adhesive is applied as a solution and its associated solvent must be driven off prior to bonding. Other methods have also been utilized.
The known methods for manufacturing such decals are costly and time consuming. Also, since the overlaminate applied to the ink and backing layers is continuous, the decals must be die cut from the continuous sheets before final use. This involves the added expense of costly dies and cutting equipment, particularly when the decal has a complex shape.
There are many other different types of labels or decals produced by various processes. One common process requires printing successive layers of inks onto a release coated paper stock and finally applyiing an adhesive. Such labels are normally printed with nitrocellulose ink systems and do not approach the strength of the laminated decals. Decals of such construction also suffer from another major disadvantage. They are printed onto a paper based substrate and they are printed by screen process. Paper substrates are heavy and generally opaque. Still the heavy substrate is necessary to allow the sheet to be printed with many layers needed to build up the strength of the decal by applying many coats of clear laquer as well as all the colors needed to achieve the graphic design.
The opacity of the substrate makes it impossible to accurately align these decals and place them precisely. Further, when such decals use a high tack adhesives, the adhesive bonds immediately upon contact and no repositioning of the decals is possible. This is particularly true with respect to the printed decals which do not have sufficient tensile strength to allow peeling and replacement.
There are still other labels that have been detailed in various patents such as Reed, U.S. Pat. No. 3,987,225 or Mackenzie, U.S. Pat. No. 3,212,913. Such labels are printed on transparent plastic substrates usually designed for making original artwork rather than being used as a final decoration although such usage is detailed in the patents. Reed and others teach the use of cellulose inks of low film thickness typically 0.003-0.0005 inches and low tack adhesives. However, these decals do not approach the strength and abrasion resistance of the laminated decals previously discussed.
Keough et al in U.S. Pat. No. 4,022,926 discloses a laminated label which is fashioned by printing a radiation polymerizable liquid onto discrete areas of a backing or carrier sheet covered with discrete areas of adhesive. The radiation process is an additional step in the manufacturing process of such decals.
Shadbolt et al in U.S. Pat. No. 4,177,309 discloses lettering sheets comprising a carrier sheet, a printing ink formulated with a resin and an adhesive over layer. However, such sheets have limited abrasion resistance and are single color letters.
The present invention is an improved decal which has improved abrasion resistance, may be printed in multicolors and which may be manufactured by use of printing techniques.